Previous work has delineated some important physical and biological features which affect biodegradation processes associated with the bioreclamation of contaminated sites. Microorganisms have been isolated from both carbon filters and contaminant plumes which exhibit diversity in species and the metabolic pathway(s) used for benzene, toluene, ethylbenzene and xylene (BTEX) degradation. In addition, studies related to the anaerobic degradation of chloroaromatic compounds suggest potential broad substrate specificity for the mechanisms associated with reductive dechlorination. This proposal incorporates knowledge gained in the previous project period towards the formulation of specific aims to further study microbial interactions attendant to bioreclamation and extends the purview of this work to studies of PAH and chlorinated aromatic compound(s) degradation as well. The major goals of Projects 0010, 0011, 0012 and 0013 are to evaluate microbial interactions in populations which contribute to the ascendancy of populations associated with biodegradation in simulated natural environments; to explore the utility of seeding BTEX contaminated soil with populations established on GAC; and to describe mechanisms for dechlorination by subcellular components of anaerobic bacteria. Particular attention will be focused on the influence of oxygen content and the influence of alternate electron acceptors on degradative processes in anoxic environments. For some projects, recombinant DNA technology will be employed to clone elements of degradative microorganisms into heterogenetic bacteria to further elucidate mechanisms associated with the regulation of these pathways. Multivariant molecular probes derived from "benchmark" microorganisms will be used to estimate population dynamics occurring during adaptation to a biodegradation process. These probes will be further utilized to study populations in simulated aquifer environments. In addition, mechanisms for reductive dechlorination will be assessed by examining the influence of natural metal-organics on the rates and extent of degradation on chlorinated organic compounds. Information from these studies will be utilized towards the optimization of in situ bioreclamation technology.